(1) Field of the Invention
This invention relates to an apparatus for the control of the idling speed of an internal combustion engine, and more particularly relates to an apparatus for the control of the idling speed of the internal combustion engine, capable of controlling the number of rotations of the internal combustion engine during an idling operation following the termination of cranking at the optimum level without being affected by change in viscosity of the engine oil, the temperature of cooling water, the temperature of the ambient air, and the load exerted on the internal combustion engine.
(2) Description of the Prior Art
The internal combustion engine used in an automobile (hereinafter referred to simply as "engine") is provided with a bypass for bypassing a throttle valve and a valve for regulating the amount of air passed through the bypass by varying the area of an opening in the bypass.
Feedback control of the number of engine rotations (RPM) especially during an idling operation of the engine has heretofore been attained by varying the area of an opening in the bypass. To be specific, in starting the cranking and after terminating the cranking, it has been customary that during the period which elapses until a stabilized idling operation is established (hereinafter referred to as "after-cranking"), the feedback control is switched to the open loop control and the area of an opening in the bypass is controlled by the amount of regulation experimentally or empirically determined in advance.
The conventional technique described above has entailed the following problem.
The number of engine rotations in-cranking and after-cranking is controlled by the open loop system using fixed values. When the engine oil is changed to that which has different viscosity or when the load on the engine is varied, therefore, the number of engine rotations during in-cranking and after-cranking becomes highly unstable.
Some grades of engine oil gain in viscosity at lower temperatures. When the engine oil previously used in the engine is changed to one of such grades of engine oil and when the temperature of the ambient air is extremely low at the time that the engine is started, for example, the engine which has been started and set operating by itself may be readily stopped or deprived of stability of rotation after stop of the starter because the amount of air fed through the bypass is insufficient.
Further, there is a possibility that the problem just mentioned will occur even at room temperature when the engine oil is fouled so much as to deteriorate the quality.